By DONALD G. McNEIL Jr.

Published: January 12, 2010

Six heroin users in Scotland have died of anthrax poisoning, and more have fallen ill, British health authorities said last week.

The suspected source of the anthrax is bone meal from Afghanistan, demonstrating how globalization of the drug trade can spread infections that were once local.

Although heroin users frequently get infections, they usually get bloodborne viruses like H.I.V. or hepatitis C from shared needles or get bacterial abscesses because their skin or the needle was not clean. In the 1990s, California had an outbreak of botulism infections in wounds, caused by ''black tar'' heroin from Mexico; as in the Scottish cases, the bacteria were also thought to be in the injection itself.

Heroin is usually diluted with other chemicals, including glucose and lactose, bicarbonate of soda or over-the-counter drugs. In this case, the authorities think Afghan middlemen used bone meal from livestock. The bacteria that cause anthrax are endemic in Afghanistan, and the meal could have contained dry anthrax spores. These can survive for decades and then blossom when they reach warm tissue like lungs, intestines or punctured skin.

While anthrax is often fatal to those who inject it, the risk to others, even close family members, is very small, British experts said, since the germs do not spread as readily as the spores do.

''Scottish police forces are investigating the source of the contamination,'' said Scotland's health secretary, Nicola Sturgeon.